Windows Live Messenger (WLM), commonly referred to by the
previous names of MSN Messenger or MSN for short, is an
advertisement-supported instant messaging client for Windows XP, Windows
Server 2003, Windows Vista, and Windows Mobile, first released on July 22,
1999 by Microsoft. It is part of Microsoft's Windows Live set of online
services. The current version is 8.1, which was released on January 29, 2007.

"MSN Messenger" (or often just "MSN") is often also used to refer to the
.NET Messenger Service (the protocols and servers that allow the system to
operate), rather than any particular client. Corporations can also integrate
their Live Communication Server and Active Directory with the network on
behalf of its clients. Most major multi-protocol clients can also connect to
the service.

Development of Windows Live Messenger

Windows Live Messenger 8.0 Beta 1

The first beta to be released to the public it included a complete overhaul
of the conversation window, with orange being the default instead of blue,
although there was the option to customize this using the paintbrush symbol.
The send and search buttons were put into different rounded boxes in the text
area. The contact list was also completely redone, so that when you hovered
your mouse over a contacts screen name, a more detailed and larger rectangle
appeared in its place. The default color was also orange, and it contained the
"Word Wheel" search box at the top, as in the final. Known bugs within this
version include the offline conversation feature: although still advertised in
the yellow bar at the top of the conversation box, it is useless to anyone who
had not received an invitation (i.e., downloaded it from another site). It
remained online and usable for about a month until an auto-update feature
forced one to install Beta 2, rendering this version obsolete.

Windows Live Messenger 8.0 Beta 2

The second beta to be released to the public replaced the newly designed
desktop icon with the Windows Messenger icon. The interface was once again
changed so the display picture, text box and conversation box were all
squared, with the default color being changed back to blue. The contact list
also contained the symbols from MSN Messenger 7.5 and earlier. It only
remained online for a couple of weeks until an auto-update feature forced one
to install Beta 3, rendering this version obsolete.

Windows Live Messenger 8.0 Beta 3

This beta was nearly identical to the final. It introduced a brand new
desktop icon not seen before, redesigned the interface to both the
conversation and contact list windows to make it more pleasing, brought back
the word wheel function on the contact list, and made the default color a
dark-blue to light-blue fade. Anyone with this beta installed on their PC can
continue to use it as of early August 2006.

Windows Live Messenger 8.0

Released June 19, 2006, this version has all features mentioned above
working, for example offline conversations, the possibility to share files
with other users, a new user interface, and much more. This version runs on
Windows XP and later.

Windows Live Messenger 8.1

This version was released from Microsoft on January 29, 2007. New features
include improvements for Windows Vista compatibility, roaming Display Pictures
and Personal Messages (which means that the Display Picture is stored on
Windows Live servers and will not change if you log in from another computer),
and support for lower bandwidth connections when attempting to use Verizon web
calling to make a PC to Phone call. Other small additions include a "Sign out"
button in the status menu, a new Messenger buddy emoticon, and new menus for
Winks, Emoticons, Backgrounds and Display Pictures. Remote desktop is still
supported but the entire desktop is shared, with no ability to select
individual applications.

The i'm initiative is also an added feature of 8.1.

Features new to Windows Live Messenger

To the features available in MSN Messenger, Windows Live Messenger adds the
following:

Sharing folders

The Sharing Folder feature of Windows Live Messenger is an
alternative to the "direct transfer" method of file distribution. When a user
wants to deliver a file to another person on his or her contact list, the
"sharing folder" window appears, which is an individualized representation of
all previously shared items.

When files are added to the "sharing folder" for that particular person,
the file will automatically be transferred to the corresponding computer when
they are online. This means that the folder is literally "shared" between two
computers. If a user deletes a file, for example, the file will also be
deleted from the corresponding computer's shared folder.

To minimize risk of virus-infected transfers, the "sharing folder" feature
is bundled with an anti-virus program. The "sharing folder" feature can only
be used on computers with NTFS-formatted hard disks.

PC-to-phone calls

In addition to PC-to-PC calls that have been supported in previous
versions, Windows Live Messenger now supports PC-to-phone calls with Windows
Live Call. This feature is supported by Verizon, branded as "Verizon Web
Calling". This feature is only available in select countries, including the
US, the UK, France, Germany, the Netherlands, Austria, Ireland, Finland,
Belgium, Spain, and Italy.

Windows Live Messenger to Yahoo!

On October 13, 2005, Yahoo! and Microsoft announced plans to introduce
interoperability between their two messengers, creating the second largest
instant messenger user base worldwide: 40 percent of all users (AIM currently
holds 56 percent). The announcement comes after years of 3rd party
interoperability success (most notably, Trillian, Gaim) and criticisms from
Google that the major instant messengers were locking their networks.
Microsoft has also had talks with AOL in an attempt to introduce further
interoperability, but so far, AOL seems unwilling to participate.

Interoperability between Yahoo! and Windows Live Messenger was launched
July 12, 2006. This allows Yahoo! and Windows Live Messenger users to talk to
each other without the need to create an account on the other service,
provided both contacts use the latest versions of the clients. However, if a
user uses an older client, they will appear offline to the users on the other
network.

Offline messaging

Unlike previous versions, one can start conversations even when his or her
status is set to Appear Offline, similar to behaviour in Yahoo!
Messenger. If talking to someone who has an older MSN Messenger client, they
will lose the ability to talk to you after a short period of no activity, due
to their client thinking you are offline.

Games and applications

There are various games and applications available in Windows Live
Messenger that can be accessed via the conversation window by clicking the
games icon and challenging your "buddy".

i'm Initiative

The i'm Initiative is a new program Microsoft launched in March 2007, that
connects the user with nine of the world's most effective organizations
dedicated to social causes through Windows Live Messenger. Every time someone
has a conversation using i'm, Microsoft Corp. shares a portion of the
program's advertising revenue with the organization of the user's choice.
There is no set cap on the amount donated to each organization. The more i'm
conversations the user has, the more money goes to one of the nine causes.
Each participating organization is guaranteed a minimum donation of $100,000
during the first year of the program. There is currently no end date for the
program. . The i'm initiative only works with the most recent WLM version 8.1.
The i'm initiative is available to those in the 50 United States and the
District of Columbia.

Other changes

The color scheme drop-down

Nicknames of individual contacts can be customized to appear differently
from what the contact has set.

Messages from contacts can now be time-stamped.

Windows Live Messenger has the ability to turn off prepending of contact
names if the same person writes multiple messages. If the same contact
writes more than one message, the contact name will be displayed for only
the first message. However, if messages are timestamped, and the time
changes, the contact's name will be displayed with the new time.

A color scheme can be chosen for the entire application, including the
status window, and not just the conversation windows. A paint brush menu is
situated below the personal message box in Windows Live Messenger, to
facilitate choosing colors.

Microsoft Passport has been replaced with Windows Live ID.

Word wheel search within the contact list.

As of version 8.1, your display picture and personal message are stored
on the server, so wherever you sign in, the display picture and message will
still appear. However, all computers must have version 8.1 for the feature
to work.

Protocol

Windows Live Messenger uses the Microsoft Notification Protocol (MSNP) over
TCP (and optionally over HTTP to deal with proxies) to connect to the .NET
Messenger Service—a service offered on port 1863 of messenger.hotmail.com. Its
current version is 15 (MSNP15), used by Windows Live Messenger and other
third-party clients. MSNP15 introduces a different authentication mechanism.
The protocol is not completely secret; Microsoft disclosed version 2 (MSNP2)
to developers in 1999 in an Internet Draft, but never released versions 8, 9,
10, 11, 12, 13, or 14 to the public. .NET Messenger Service servers currently
only accept protocol versions from 8 and on, so the syntax of new commands
from versions 8 through 14 is only known by using sniffers like Wireshark.

Competition

The most significant rivals of Windows Live Messenger are AIM and ICQ (both
from AOL), Skype, Pidgin (formerly Gaim) and Jabber based clients including
Google Talk.

In China, an instant messenger named QQ is predominantly used. Although
used little outside of China, its domestic users number as many as 226
million. However, its popularity has recently been greatly weakened, since the
entering into the Chinese market of MSN Messenger. Up until now, MSN Messenger
has taken about 17 percent of the Chinese market.